Influence of the back-stress effect on the interstep distance and on the surface supersaturation

Abstract

The back-stress effect is a reduction of local supersaturation in the centre of growth spiral caused by the presence of the rest of spiral step. The interstep distance approximations differ from one another in estimations of this effect. The influence of the interstep distance approximations on calculated supersaturation existing on the surface of growing crystal is analysed on the basis of the BCF surface diffusion theory. The analysis reveals that, although the back-stress effect does not essentially change the shape of the R( σ) curves, it affects strongly the surface supersaturation existing on the step terrace. It is shown that the back-stress effect should be taken into account even at low bulk supersaturations. A new modification of the Cabrera–Levine approximation for interstep distance is proposed. Replacing of bulk supersaturation by the theoretically found surface supersaturation makes the modified Cabrera–Levine approximation usable for both very low and higher bulk supersaturations.